Groundwater modelling with MicroFEM • Lesson 9A: 3Dflowlines 
Load the model of lesson 8 (click Lesson 8.fpr)
We will show how to draw 3D flowlines. Before starting with this, we need: A starting point requires the x, y and zcoordinates of a point somewhere in the model. MicroFEM uses the x and ycoordinate of the current node. The zcoordinate is given in a different way. The flowline starts in the aquifer indicated by the active cell in the Param Table. There is only one aquifer in our model. We select H1 (T1 or Q1 have the same effect). The zcoordinate also depends on the depth within that aquifer. This has to be specified as a "dimensionless depth". A dimensionless depth of 0 means at the upper boundary of that aquifer, 1 means at the base of that aquifer and 0.5 means right in the middle. A dimensionless depth can be any value on the interval [0 ... 1].
Drawing mode / [Del] / [F2] / Click at a node near (2000, 3000) Select H1 in the Table / [Draw flowlines (F9)] A window appears "Drawing 3dimensional flowlines". Possible settings are:
By selecting Forward and Level = 0 we indicate that we start at the water table and go with the flow. (An alternative way to start at the water table is to select H0; the Level is not required then).
Check that "Forward" is selected and that Levels = 0 / [OK] The 3D flowlines window disappears. A yellow flowline is drawn in the map. When counting the dots, the travel time must be between 50 and 60 years. Zooming is allowed.
[F10] / [F12]
In the map the yellow Profile line is bordered by two parallel red lines. Any 3D flowline between the red lines will be projected on the vertical 2D plane of the Section. In the left (western) part of the Section the same flowline with time steps is displayed in white. Zooming in the Section is also allowed (start with rightclick).
[F10] / [F12] / Click a node at the model boundary, just north of the flowline / H1 / [F9] Backward / Time step = 1 / Level = 0.5 / [OK] [F10] / [F12]
The computation of the new flowline starts at a depth of 5 m. The line is computed Upstream. It represents a rain drop that infiltrated some 800 m east of the boundary. Travel time 6 or 7 years. Here are some further details about 3D flowlines: One or more flowlines:
Flowline files:
Colour of flowlines:
Save the model.
